Television scanning apparatus



Aug. 13, 1940. R URTEL 2,210,992

TELEVISION SCANNING APPARATUS Filed Sept. 21, 1936 r I I ""P ----P I a, a a z, z z 2 3 I 1 1 2 2 E 3 3 i w I INVENTOR ATTORNEY Patented Aug. 13, 1940 UNITED STATES TELEVISION SCANNING APPARATUS Rudolf Urtel, Berlin, Germany, as'signor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application September 21, 1936, Serial No. 101,815 In Germany September 21, 1935 i 2 Claims.

The invention relates broadly to a system for operating a plurality of television image scanhers and more particularly to a system in which a plurality of scanning devices are arranged to operate selectively and which are so arranged that the ray is deflected by a common deflection potential generator. Such an arrangement when used with cathode ray type image scanners is of particular advantage in view of the fact that in the course of a long television transmission, the scene may pass from one image scanner used, for instance, for the transmission of a film to an-' other scanner which may, for instance, scan a stage scene, an open-air scene, or the like. Ac-

cording to my invention, the transit from one scanner to another may be carried out without receivers dropping out of step such as may occur if the scanners were operating entirely independently of each other.

An embodiment according to the invention in which the common deviation means or, as will be referred to hereinafter, as a common rhythm plication.

Referring to the drawing, a1, a2, 03 represent a cathode ray type image scanner, and T is a rhythm indicator common to all scanners, and which supplies the impulses for the production of the horizontal and vertical deflection of the cathode ray. Each of the scanners m to as is equipp d with a modulation arrangement m1, m2, mg each of which is fed by a carrier frequency generator t1, t2, t3. Across each respective receiver of the control image in, kg, ha likewise connected to the common rhythm indicator T across the lines Z1, Z2, Is the scanning currents pass to a switch U in back of which a rectifier G is arranged. The

, latter demodulates the carrier frequency currents obtained from the modulators 1m to ms, and it is connected to another modulation arrangement M. Within this latter arrangement, the carrier wave furnished by the carrier frequency generator t is controlled in the one sense in accordance with the image content, and in the other sense according to the impulses produced by the rhythm indicator T. The modulator M may operate in such a manner, for instance, that a finite carrier wave amplitude is assigned to the black parts of the image, while at the brighter parts of the image the carrier wave amplitude increases. The synchronizing impulses are then transmitted by a decrease in the carrier wave amplitude below the value assigned to the aforementioned black image parts. This reduction in amplitude can, if desired, be extended down to the 'zero value. In back of the modulator M a further control image receiver K is arranged by means of which the modulated currents having the frequency t and by which the cable or the high-frequency transmitter is to be supplied, can again be controlled.

The arrangement shown in the figure is insofar especially distinctive since it afiords a distribution in a suitable manner of the control of the transmitted currents over several places. In fact, when handling the individual scanners m to as no consideration needs be given to the value of the image level in its proportion to the synchronizing impulse, the setting of the proper level can, in fact, be exclusively carried out at the modulators M.

The transmission of the image from the individual scanners al to as to the modulator M is carried out eventually and suitably by means of difierent carrier frequencies 151 to is in order thereby to exclude a mutual influence of the transmission lines between the modulators 1m to m3 and the switching contacts. Eventually, it may also be advisable to insert phase displacing devices in several or in allpoints of the lines, so as to insure the proper position of the synchronizing impulses in the'line and image intervals of the image transmission.

If the carrier frequency generator t has a substantially higher frequency than the carrier frequency generators in to is at the individual scanted, and the carrier wave T can be modulated directly with the currents coming from the switch U.

What ,I claim is:

1. In a television transmission system, a plu-. rality of cathode ray scanning means, a plurality of carrier wave generators, means for modulating each of said generators in accordance with the optical values impinging on each of said cathode ray scanning means, means for selectively transmitting said values from one of said scanning means, and means for generating deflecting energy common to said plurality of cathode ray means. I

2. In a television transmission system, a plurality of cathode ray scanning means, a plurality of carrier wave generators, means for modulat- 

